Martino: I did nothing for Barcelona
Martino left Barcelona at the end of the 2013-14 season - less than a year after replacing Tito Vilanova - having failed to win a trophy apart from the Spanish Super Cup.
The 52-year-old Argentine has gone on to become his country's senior coach but, in an interview with Argentine newspaper Clarin, it is clear his experience in the Catalan capital still rankles.
When asked what he had taught Lionel Messi - who he still works alongside with Argentina - Martino said: "Nothing. Nothing at all. Not to him or to Barca."
Martino added: "I am just being critical with myself about what happened when I was there.
"I left nothing at Barca, it was a blip in my career - it turns out that it happened in the most important place I have worked at."
Prior to his time with Barcelona, Martino helped his home-town club Newell's Old Boys to their first Argentine Primera Division title in nine years, while he has also won Paraguayan Primera Division titles with Libertad and Cerro Porteno.
Failing to add any significant silverware to the trophy cabinets at the Camp Nou does not sit well with the Rosario-born coach.
"I made some terrible mistakes; I felt as though I was a better coach after my time at Newell's but at Barca, the only thing I learned was how to be amongst superstars, the best players in the world," Martino said.
"I joined a club who had always won but, under me, they didn't win anything.
"For Barcelona, winning the Spanish Supercup doesn't really mean anything."
Under Martino's replacement Luis Enrique, Barcelona sit second in La Liga, one point adrift of Real Madrid and three ahead of title-holders Atletico Madrid, ahead of the second half of the season.
Barcelona finished second in the Spanish top flight last term, while they lost the Copa del Rey final to Real.
Martino said his biggest achievement was helping Alexis Sanchez reach a new level but he appreciates that did not help Barcelona much, as the Chilean forward is now at Arsenal.
"I don't think I'm being tough on myself - I'm just saying what I feel," he said.
"I could lie and say it was amazing or that I turned [Andres] Iniesta, Messi and Neymar into better players but it wasn't like that.
"Of course I did make some contributions, I did hand Alexis Sanchez more minutes than he had been getting but he ended up leaving the club."